SIEMENS SIMATIC S7-300 Beginner's Guide

SIEMENS SIMATIC S7-300 Beginner's Guide

The Siemens SIMATIC S7-300 Beginner's Guide (version 04/2007) takes conveyor belt motor control as an example and provides a detailed introduction to the entry-level operation of adapting CPU 312C (order number 6ES7312-5BE03-0AB0). The core process includes preparing a PC (installing STEP 7 Lite V3.0+SP2 and PC Adapter USB driver), installing wiring hardware components, configuring control in STEP 7 Lite, downloading programs, and executing test runs. The entire process must comply with electrical safety regulations and support motor start, direction switching, and stop functions. The overall operation time is about 1 hour, suitable for users with Windows operation and electrical basic knowledge.

Basic information of the document

Core positioning: A beginner's guide to S7-300 for beginners, explaining the complete process of PLC from hardware installation to program operation through an example of conveyor motor control

Key adaptation: Only applicable to CPU 312C (order number 6ES7312-5BE03-0AB0), requires SIMATIC Micro Memory Card (MMC), starting firmware version V2.6

Safety reminder: Clearly distinguish the four levels of "danger/warning/caution/attention" safety, emphasize that only qualified professionals are allowed to operate, and comply with safety standards such as IEC 204

Preparation in advance

Skill Requirements

Proficient in operating Microsoft Windows operating system

Master the basic knowledge of electronic and electrical engineering

List of Materials and Tools (Core Components)

|Category | Project | Order Number (Siemens) | Quantity | Remarks|

|Core module | CPU 312C | 6ES7312-5BE03-0AB0 | 1 | Integrated DI10/DO6, requires MMC card|

|Power Supply | Power Module | 6ES7307-1EA00-0AA0 | 1 | Provides DC 24V power supply|

|Installation accessories | Installation track | 6ES7390-1AB60-0AA0 | 1 | M6 screw is required to fix the grounding|

|Connection accessories | PC Adapter USB | 6ES7972-0CB20-0XA0 | 1 | MPI interface with driver program for connecting PC and CPU|

|Front connector | Screw type multi terminal front connector | 6ES7392-1AM00-0AA0 | 1 | Compatible with CPU wiring|

|Control element | Instantaneous contact switch | - | 4 | 24V/2A, used for motor start stop and commutation|

|Software | STEP 7 Lite | - | 1 | V3.0+SP2, available for free download|

|Tools | Screwdrivers, wire strippers, crimping tools, etc. | - | Several | Market procurement, including 3.5mm/4.5mm blade screwdrivers|

|Cable | Grounding cable (10mm ²), flexible cable (1mm ²), etc. | - | As needed | Grounding cable needs to be compatible with M6 screws|

Core operational process (step-by-step)

1. Prepare PC (software and interface settings)

Install STEP 7 Lite: from the official website（ http://support.automation.siemens.com ）Download and follow the wizard to complete the installation

Install PC Adapter USB driver: Insert the driver CD and follow the prompts to install

Set PG/PC interface: Select "PC Adapter (MPI)", configure USB connection, enable MPI communication between PC and CPU

2. Hardware installation and wiring

Installation track: fixed with 2 M6 screws, grounding cable cross-sectional area ≥ 10mm ², leaving a gap of ≥ 40mm above and below the track (for heat dissipation and operation)

Installation module: First install the power module (fixed by hand), then install the CPU 312C, and insert the front connector (not locked temporarily, convenient for wiring)

Wiring operation:

Prepare the cable: Cut it to the desired length, strip off the insulation layer, and put on a 6mm insulation ring

Wiring sequence: power supply → CPU 312C → momentary contact switch (connected to DI terminal) → motor (connected to DO terminal, optional)

Key requirement: Cut off the power before wiring, and set the line voltage selector correctly

Hardware debugging:

Connecting PC and CPU: Connect PC Adapter and PC with USB cable

Power on test: Insert the MMC card, set the CPU to STOP mode, and turn on the power (power DC24V LED lights up, CPU DC5V and STOP LED lights up)

Test wiring: Press the momentary contact switch and observe whether the corresponding CPU input LED lights up (such as the input 0.0 terminal LED corresponding to the start switch)

3. Software Configuration (STEP 7 Lite)

Open project: Start STEP 7 Lite and open the instance project "converyor.k7p"

Create module configuration:

New S7-300 station, automatically generate 4 installation tracks

Insert the power module (such as 6ES7307-1BA00-0AA0) and CPU 312C, and it will automatically display in the hardware view and configuration table

Set CPU parameters: Set the reserved bit storage quantity to "0" to avoid motor runaway startup after power failure

Establish online connection: When STEP 7 Lite starts, it automatically attempts to connect and the status bar displays "STOP" (connection successful) or "Disconnected" (manual connection required)

Download configuration: First, perform a CPU memory reset (delete old programs/configurations), then download a new configuration and check the consistency of offline/online configurations

4. Program operation and test run

Open program: The program in the project is stored in OB1 (Organizational Block 1), written using ladder logic (LAD), and includes 4 network segments (clockwise/counterclockwise/start/stop)

Download project: Download hardware configuration and OB1 program to CPU 312C, confirm to overwrite existing configuration/program

Test Run:

Switch CPU mode: Set the mode switch to "RUN", and the RUN LED will change from flashing to constantly on

Functional testing:

Start: Press the green momentary contact switch, input 0.0 LED briefly on, output 0.3 LED constantly on (motor ready)

Clockwise rotation: Press and hold the corresponding switch, input 0.2 LED lights up, output 0.0 LED lights up

Counter clockwise rotation: Press and hold the corresponding switch, input 0.3 LED lights up, output 0.5 LED lights up

Stop: Press the red momentary contact switch, input 0.1 LED briefly on, output 0.3 LED off